In vitro exposure of red cells to vie International Union against Cancer (UICC) standard reference asbestos samples resulted in an increase of thiobarbituric acid substances. Chrysotiles developed the largest amounts of lipid peroxides, followed by anthophyllite, amosite, and crocidolite in decreasing order. Compared with the control samples erythrocytes free of dusts, all types of the asbestos examined disclosed significant differences. The results obtained provide support for the cytotoxic potential of amosite and crocidolite and, on the other hand, suggest that a lipid peroxidation of unsaturated fatty acids may be involved in the mechanisms(s) of membrane-damaging effects of asbestos dusts.